Method of preparing cellular glass



Nov. 25, 1941. w. o. LYTLE 4,

METHOD OF PREPARING CELLULAR GLASS Original Filed Nov. 8, 1957W/L-LIHMQLV'TLE Patented .Nov. '25, 1941 UNITED STATES PATENT OFFICE2,264,246 ME'rnon or PREPARING CELLULAR GLASS William O. Lytle, NewKensington, Pa., assignor to Pittsburgh Plate Glass Company, AlleghenyCounty, Pa.,.a corporation 01' Pennsylvania Original applicationNovember 8, 1937, Serial No.

4 173,390, now Patent No. 2,237,037, dated April 1, 1941. Divided andthis application September 21, 1940, Serial No. 357,723

1 Claim. (0149-77) The present invention relates to the manufacture ofglass products and it has particular relation to the production ofbodies of multi-cellular or porous glass. One object of the invention isto provide a process of preparing a multi-cellular glass in which thecells are uniformly distributed and which does not require the additionof gasifying agents to the glass in order to produce the cells orvesicles.

A second object of theinvention is to provide a process of preparingmulti-cellular glass by use of which relatively large quantities of suchglass can be formed by continuous operation into a slab of suitablethickness to be cut upintostructural blocks.

These and other objects will be apparent from consideration of thefollowing specification and claim. a

It has heretofore been proposed to form blocks of multi-cellular glassby admixture of carbonaceous-material with molten glass, therebyinducing a chemical reaction to liberate free gases such as carbon dio'de as bubbles or vesicles in the glass. The mas' was then placed insuitable molds and allowed to expand to fill the latter after which theresultant blocks were cooled and removed. The multi-cellular product wasof relatively low apparent specific gravity and possessed heat and soundinsulating properties.

Such process was objectionable for many 4 reasons, for example, thecarbonaceous material was more or less e e to obtain. Uniformdistribution of the gassing agent in the viscous.

- feature of the invention involves the extrusion of the plastic masscontaining the bubbles'of reference may nowbe had to the drawing inwhich the single figure, is a cross-sectional view of a simpleembodiment of apparatus suitable for use in practicing the invention.

In theform of the invention disclosed, a column-like chamber orcontainer l0 (preferably of a relatively heat resistant material and ofsufficient strength to resist considerable internal pressure) isdisposed in a furnace ll heated by suitable means, for example, byconventional gas burners l2. At'its upper extremity the container isprovided with an inlet I3 for the admission'of crushed or pulverizedglass communicating with a chamber l4 that constitutes an air lock dwhich further'communicates with a hopper l li. Slide valves I6 and I!close the passage l3 and the throat of hopper IS. A conduit It for theintroduction of air or other suitable fluid also projects into the upperextremity oithe chamber and may be closed by means of a valve IS. Thebottom portion 20 of the container tapers and curves laterally through,the side of the furnace to a tip having anorifice 2| of appropriate size.and shape for the extrusion of the sintered or molten glass, whichorifice is closed by means of a suitable slide valve 22. The materialcharged with. gas under compression as it emerges from the orifice isdischarged upon a table or a con- 7 exerts aconsiderable mechanicalpressure on the 1 material in the lower portions thereof, thus tend thepressure is raised to sufllcient value to give thedesired ratio of gasesdissolved in particles compressed or dissolved gases through an orificeof such dimensions as to impart thedesired cross-sectional contour tothe mas. The extruded body may then be cooled and annealed 3ndafterwards cut into sections of suitable length.

For a better understanding of theinvention F.) to sinter or melt theparticles of glass down i into acoherent but porous or cellular state inwhich each cell is filled withgas under comm-es.

sion. The/"valve 22 in orifice 2| is then opened and thecellular glassis forced out by fluid pressure as a viscous mass upon the table 23.Upon emergence from the pressure vessel the gases contained as vesiclesor bubbles in the plastic glass tend to expand and therebyincr'ease theporosity of the mass. annealed-and cut into blocks of suitabledimensions. If the orifice 2| is of proper size and shape the stream ofglass after it has expanded will correspond approximately to the crosssectional dimensions of the finished blocks.

After the material in the chamber is partially or completely discharged,fresh pulverized glass is charged from hopper l5. This is accomplishedby opening the valve l'l while valve I6 is closed in order to permit thecontents of the hopper l5 to fall into the intermediate chamber I4. The

valve I1 is then closed to seal the .chamber ll from the atmosphere, thevalve [6 is opened to permit the glass to fall into container l0 andvalve I6 is closed. The chamber I0 may thus be charged without releasingthe pressure th'erein Subsequently the glass is lease of pressure uponthe glass tends further to increase the volume of bubbles generated inthe latter. Manifestly, the size of these bubbles formed by theabsorption and expansion of the glass. Upon release of the pressure, thegases occluded in the glass will expand the latter to fill ..the mold orchamber. After the glass is cooled and without interrupting the flow ofmaterial from orifice 2 I The product obtained will comprise a mass ofvesicular glass of low apparent density in which the voids or cells arequite uniformly distributed.

By increasing or decreasing the pressure employed in the melting chamberthe degree otex pansion and therefore the density of the mass can becontrolled at will.

Obviously, water or other suitable fluid may be admixed with the culletbefore introduction, or may be introduced into th'e vessel after theintroduction of the cullet. Long prior to the melting or sintering ofthe granular glass the water is completely converted into steam and actsas a gaseous medium for the formation of bubbles in the glass.Considerable amounts of the water are absorbed rather than being merelyoccluded in the glass and this absorbed water .upon resuiiiciently, itmay be removed.

Although the preferred forms of the invention have been shown anddescribed it will be apparent to those skilled in the art that numerousmodifications may be made therein without departure from the spirit ofthe invention or the scope of the appended claim.

This application is a division of copending application Serial No.173,390, filed November 8, 1937, which issued as Patent No. 2,237,037,dated April 1, 1941. V

What I claim is:

A method of preparing multi-cellular glass which comprises introducingcrushed glass into a column-like container, filled with a gaseousmedium, under relatively elevated pressure, heating the glass to atemperature suflicient onl partially to fuse the surface of theparticles together,

thereby to partially coalesce the particles of glass into a porous massand to entrap the gaseous medium between particles, then forcing themass through an orifice approximately at the bottom of the containerinto a zone of relatively reduced pressure toexpand the pores thereinand subsequently annealing the resultant vesicular glass.

% WILLIAM o. LYTLE.

